Electrochemical Characterization of Polyelectrolyte/Gold Nanoparticle Multilayers Self-Assembled on Gold Electrodes

Abstract

Polyelectrolyte/gold nanoparticle multilayers composed of poly(L-lysine) (pLys) and mercaptosuccinic acid (MSA) stabilized gold nanoparticles (Au NPs) were built up using the electrostatic layer-by-layer self-assembly technique upon a gold electrode modified with a first layer of MSA. The assemblies were characterized using UV-vis absorption spectroscopy, cyclic and square-wave voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy. Charge transport through the multilayer was studied experimentally as well as theoretically by using two different redox pairs [Fe(CN) 6 ] 3-/4-and [Ru(NH 3 ) 6 ] 3+/2+ . This paper reports a large sensitivity to the charge of the outermost layer for the permeability of these assemblies to the probe ions. With the former redox pair, dramatic changes in the impedance response were obtained for thin multilayers each time a new layer was deposited. In the latter case, the multilayer behaves as a conductor exhibiting a strikingly lower impedance response, the electric current being enhanced as more layers are added for Au NP terminated multilayers. These results are interpreted quite satisfactorily by means of a capillary membrane model that encompasses the wide variety of behaviors observed. It is concluded that nonlinear slow diffusion through defects (pinholes) in the multilayer is the governing mechanism for the [Fe(CN) 6 ] 3-/4-species, whereas electron transfer through the Au NPs is the dominant mechanism in the case of the [Ru(NH 3 ) 6 ] 3+/2+ pair.

Charge Transfer Within Multilayered Films of Gold Nanorods

“…Moreover, the overall electrochemical process is strongly dependent of the nature of the outermost layer. This dependence of the electrochemical process on the nature of the outermost layer has been observed for the first time at mercaptosuccinic stabilized gold nanoparticle (Au-MSA)/poly-Lysine multilayers self-assembled on gold electrodes (Chirea et al, 2005). The difference between these two types of multilayers is in the nature of the interaction between the redox probes in solution and the outermost layers.…”

“…In our previous work (Chirea et al, 2005), the depressed semicircles observed in the EIS spectra were due to a repelling effect (electrostatic repulsion ) between the outermost layers of negatively charged gold nanoparticles (Au-MSA NPs) and negatively charge redox probes ([Fe(CN) 6 ] 3-/4-) in solution. It has to be mentioned also that the electron transfer was mediated by the Au-MSA NPs when they were covered by a positively charged poly-Lysine layer which facilitated the diffusion of the electroactive species through the film based on electrostatic attraction.…”

“…The electrochemical cell was placed in a Faraday cage in order to minimize the electrical noise. The gold electrodes were cleaned as previously explained (Chirea et al, 2005) and consecutively modified following the procedure used for the QCM experiments. The electrolyte solution consisted of 0.0005M [Fe(CN) 6 ] 3-/4-and 0.1NaClO 4 .…”

“…Various electrochemical techniques have been use for the investigation of the electron transfer processes taking place at hybrid nanostructured modified electrodes. Cyclic voltammetry, electrochemical impedance spectroscopy, square wave voltammetry, differential pulse voltammetry, potential step chronoamperometry and rotating disk electrodes are among the most used techniques for these electrochemical studies (Chen &Pei, 2001;Chirea et al, 2005Chirea et al, , 2007Hicks et al, 2002, Horswell et al,2003. Electrochemical impedance spectroscopy (EIS) has been proven as one of the most powerful tools for the investigation of interfacial electrode reaction mechanisms (Katz & Willner, 2003, Yan & Sadik, 2001, Lasia, A.…”

Ion Transfer in Layer-by-Layer Films

“…EIS has been one of the primary techniques to characterize the electronic communication of the analyte with the modified electrodes. [36][37][38][39][40][41] Recently, Calvo et al demonstrated the use of EIS in measuring ionic diffusion coefficients in pyridine derivatized (PAH│PSS) multilayer films. 42 Other advances also include EIS studies for explaining catalytic and charge storage efficiencies of LbL assembled nano-scale species such as gold, [43][44][45] titanium dioxide, 46 vanadium pentoxide, 40 polyoxometalates, 47 and carbon nanotubes.…”